Global prevalence, mortality, and main characteristics of HIV-associated pneumocystosis: A systematic review and meta-analysis

The epidemiology of Human Immunodeficiency Virus (HIV)-associated pneumocystosis (HAP) is poorly described on a worldwide scale. We searched related databases between January 2000 and December 2022 for studies reporting HAP. Meta-analysis was performed using StatsDirect (version 2.7.9) and STATA (version 17) according to the random-effects model for DerSimonian and Laird method and metan and metaprop commands, respectively. Twenty-nine studies with 38554 HIV-positive, 79893 HIV-negative, and 4044 HAP populations were included. The pooled prevalence of HAP was 35.4% (95% CI 23.8 to 47.9). In contrast, the pooled prevalence of PCP among HIV-negative patients was 10.16% (95% CI 2 to 25.3). HIV-positive patients are almost 12 times more susceptible to PCP than the HIV-negative population (OR: 11.710; 95% CI: 5.420 to 25.297). The mortality among HAP patients was 52% higher than non-PCP patients (OR 1.522; 95% CI 0.959 to 2.416). HIV-positive men had a 7% higher chance rate for PCP than women (OR 1.073; 95% CI 0.674 to 1.706). Prophylactic (OR: 6.191; 95% CI: 0.945 to 40.545) and antiretroviral therapy (OR 3.356; 95% CI 0.785 to 14.349) were used in HAP patients six and three times more than HIV-positive PCP-negatives, respectively. The control and management strategies should revise and updated by health policy-makers on a worldwide scale. Finally, for better management and understanding of the epidemiology and characteristics of this coinfection, designing further studies is recommended.


Introduction
Pneumocystis pneumonia (PCP) is a serious pulmonary infection caused by a ubiquitous opportunistic fungal pathogen, Pneumocystis jirovecii [1].Humans are the main reservoir of P jirovecii, and inhalation of air-borne particles is the main transmission route [2].PCP is extremely rare in healthy people, and P.jirovecii can live in the lungs without causing symptoms [3].Exposure to this pathogen is very high [4].More than 80% of children in developed countries commonly show antibodies against P.jirovecii [5,6].Up to 20% of adults might carry this fungus at any given time, although the immune system removes the fungus after several months [7].In 1980 PCP was introduced as a substantial public health problem [8].
The prevalence of PCP escalated following the Human Immunodeficiency Virus (HIV) epidemic in the 1980swhen HIV was diagnosed in a group of homosexual men, hemophilia patients, and recipients of blood products.Although, genetic analysis revealed that the virus was first transmitted to humans around 1908 from chimpanzees polluted SIV virus, probably through the wounds of African people who slaughtered chimpanzees for food.The emergence and increase of the risk factors between 1908 and 1980 led to the HIV epidemic in 1980 [9]. PCP is almost exclusively seen in individuals with compromised immune systems by HIV/ (Acquired Immunodeficiency Syndrome) AIDS.In addition, other immunocompromising statuses include cancer chemotherapy, organ transplantation, long-term corticosteroid therapy, chronic lung diseases, and inflammatory or autoimmune diseases (for example, lupus or rheumatoid arthritis) from PCP leading factors [4,10,11].Also, it causes life-threatening pneumonic disorders in neonates [12].HIV/AIDS is the main risk factor for 30-40% of PCP cases around the world [13].PCP is usually a terminal event in HIV/AIDS patients, and much of the information we have about this infection comes from caring for patients with HIV/ AIDS [14].
Recognition of at-risk patients is based on the severity of clinical symptoms(fever, cough, difficulty breathing, chest pain, and tiredness) in high-risk populations [15].However, radiological examination and specific polymerase chain reaction (PCR) assay in sputum, bronchoalveolar lavage (BAL), tissue biopsies, and serum β-D-glucan levels (a part of the cell wall of many different types of fungi)should support the diagnosis of PCP [16][17][18].Liu et al. [19] investigated the technical advantages of molecular methods, especially PCR-based methods, for the detection of P. jirovecii among BAL fluid specimens.
Without treatment, PCP can lead to severe uncontrolled consequences in the health status [8].Trimethoprim/sulfamethoxazole(TMP/SMX), also known as co-trimoxazole, is used for PCP treatment and prophylaxis in HIV and non-HIV populations [20][21][22].Recently, progressive achievements in designing antiretrovirals have decreased the prevalence of HIV-associated PCP (HAP) [23].The mortality rate of PCP is elevated due to the abrupt occurrence of respiratory failure and delay in diagnosis [24,25].
Here, we designed this analysis to provide accurate statistics of AIDS-defining PCP.The results of our study will be suitable for researchers and health policy-makers to manage and develop preventative strategies for infection control.

Search strategy
The present study is conducted and reported according to PRISMA 2020 guideline [26] (S1 Checklist).We developed a broad search strategy to identify studies that reported PCP among HIV/AIDS population.In our systematic review, the search terms "HIV/AIDS,""HI-V,""AIDS,""Pneumocystis,""Pneumocystis jirovecii,""pneumocystosis,""Human Immunodeficiency Virus,"and related terms and words for relevant studies published in PubMed, Web of Science, Scopus, Google Scholar, and ProQuest between January 2000and December 2022 were used.No linguistic or geographical limits were applied.We handsearched bibliographies of all recovered articles for potentially eligible studies and contacted corresponding authors for published or unpublished data if needed.January 2000 was chosen as the cut-off because we aimed to assay studies published during the past 22 years.

Selection criteria
Titles and abstracts of references were screened, and the full texts of potentially relevant articles were independently assessed.Studies assessing a clearly defined population of HIV/AIDS and PCP in any clinical setting were included if they had specific diagnostic criteria for PCP.These were predefined using clinical case definitions [27] or confirmation with laboratory testing using molecular assays, such as PCR, sequencing, and matrix-assisted laser desorption-ionization time of flight mass spectrometry (MALDI-TOF MS) [16][17][18].Inclusion criteria were as follows; patients with HIV/AIDS and PCP, all types of studies encompassing data about patients with HIV/AIDS and PCP infected simultaneously, including clinical trials, retrospective, prospective, and cohort studies, gray literature including conference reports, etc. Exclusion criteria were as follows; patients with HIV/AIDS and without PCP or patients who have other fungal infections than pneumocystosis, all review type studies (e.g., narrative, critical, systematic, and meta-analysis, and mini-reviews) case reports and case series, all studies including letters to the editor, and editorials, without patient data.

Data extraction
Three authors independently extracted data and compared it for consistency.Discussion and consensus resolved disagreements on final inclusions.The key variable was the proportion of PCP coinfection among the HIV/AIDS population.Prevalence was defined as the number of PCP cases (nominator) among patients with established HIV/AIDS(denominator).The following information was captured where available; PCP among HIV-negative patients, underlying risk factors, PCP prophylaxis, antiretroviral therapy, age and gender of the target population, laboratory parameters (e.g., serum levels of CD4 + T cells, β-D-glucan, and lactate dehydrogenase), and the outcome of patients (death or survival).

Risk of bias (quality) assessment
This research involved studies concerning a minimum of three participants to minimize the small-study effect.Authors independently assessed the quality according to the Hoy et al. checklist previously described [28,29].This checklist explored the various dimensions of empirical proof and methodological assumptions.If required, a consensus was voted by other coauthors to settle the disputes between the investigators.Moreover, the regression-based Egger, Begg's-Mazumdar, and Harbord tests for small-study effects will apply to analyze publication bias for our search [30].

Data analysis
Meta-analysis was performed according to the DerSimonian and Laird method [31,32], applying the random-effects model [33] in case of considerable heterogeneity, defined as I 2 >75%.We evaluated heterogeneity using the chi-square (χ 2 -based Q statistic, significant for Pvalue0<0.5)and the I 2 statistic.StatsDirect version 2.7.9 (StatsDirect Ltd, Wirral-UK)and STATA version 17 (STATA corporation, USA) were used to perform calculations and the meta-analysis [34,35].Analysis via STATA was performed using the metan and metaprop commands [36,37] for standard mean difference (SMD) calculation.Odds ratio (OR) analysis was performed for related data if their case(s) and control(s) details were available.Point estimates and 95% confidence intervals were derived using prevalence data from included studies for all outcomes.Where standard errors (SE) were not provided, we incorporated confidence intervals into the formula, SE = (upper limit-lower limit)/3.92.Subgroup analysisand metaregression were used to determine the source of heterogeneity based on certain putative moderator factors, and sensitivity analysis was used to assess the reliability of our pooling results.

Results
After searches in the databases and removing duplicate and irrelevant records, our meta-analysis included fifty-five eligible studies (_((((xxx))))_)  (Table 1; Fig 1).The results of the quality assessment were added to Table 1.The overall score of 4.378 was reached for quality assessment, which means analyzed studies had a moderate risk of bias (Table 1).A total of38,554HIV/AIDS patients were included, and PCP was found in 2,880of them.Also, 4,044 PCP cases were reported among 79,893 HIV/AIDS-negative patients.
Almost all analyzed studies targeted respiratory tract samples to detect PCP among HIV/ AIDS patients.In some cases, serum specimen was targeted.Different diagnostic methods, e. g., conventional and real-time PCR, targeting mitochondrial small and large subunits (mtSSU and mtLSU), fast-track diagnostic (FTD) methods capturing β-D-glucan, and microscopical diagnosis were applied.

The relationship between HIV/AIDS and susceptibility to PCP
The results of the random effect model in twenty-nine included studies [38][39][40]45

Discussion
Before the beginning of the HIV/AIDS epidemic in the 1980s, PCP was uncommon.But soon became one of the major AIDS-defining illnesses in the world.Also, during the COVID-19 pandemic, PCP, known as a COVID mimic, caused major health problems alongside superinfection [93,94].Liu et al. performed two valuable studies about the host immune responses to COVID superinfection [95,96].These studies indicated that immunity triggered by SARS--CoV-2 may restrict the pathogenicity of the second post-COVID infection, such as PCP.Also, several cytokine biomarkers may be the same in these two infections, alongside the clinical sign & symptoms.In the late 1980s, 75% of people living with AIDS developed PCP [97].A study estimated the prevalence of HIV/AIDS in the U.S. and Canada, PCP was the most common opportunistic infection during 2008-2010 [98].There were 10,590 hospitalizations due to PCP in the U.S. in 2017 [99].Moreover, PCP is also a common opportunistic infection among people living with HIV/AIDS in developing countries [99].Although the prevalence of HAP has significantly decreased due to ART and prophylactic therapy with TMP/SMX, it remains a public health concern [98,100].
Unfortunately, we did not find a meta-analysis study that reports the global prevalence of HAP to compare with our results.However, two meta-analysis studies investigated the prevalence of PCP among HIV-positive adults in Africa [101,102].Wasserman et al. [101] studied 6,884 individuals from 18 countries in sub-Saharan Africa.The pooled prevalence of PCP among 6,018 patients from all clinical settings was 15.4% (95% CI: 12.9 to 18.0) and was highest amongst inpatients, 22.4% (95% CI: 17.2 to 27.7).They resulted that there was a trend of We resulted that the mortality rate increased by 52% in HAP patients compared to the HIV-positive PCP-negative population (OR: 1.522; 95% CI:0.959 to 2.416) (Table 2).Wasserman et al. [101] resulted an 18.8% (95% CI: 11.0 to 26.5)case fatality rate that PCP accounted for 6.5% (95% CI: 3.7 to 9.3) of their study deaths.Sonego et al. [103]  We resulted that HIV/PCP-positive patients received PCP prophylaxis six times more than HIV-positive PCP-negative cases (Table 2).The main prophylactic agent in our analyzed studies was TMP/SMX.Although there was a lack of meta-analysis studies about the status of prophylactic agents' consumption in HAP patients [104], we found three meta-analysis [105][106][107] of adjunctive corticosteroid therapy in these patients; however, we excluded one [105] due to the same authors' list and published study.Bucher et al. [104] reported the suitable outcomes of TMP/SMX on 1,448 HIV/PCP-positive patients and indicated that TMP/SMX decreased the risk ratio (RR) of PCP (versus aerosolized pentamidine: RR:0.59; 95% CI: 0.45 to 0.76&versus dapsone/pyrimethamine: RR:0.4995%CI: 0.26 to 0.92).Briel et al. [106] resulted that RR for overall mortality for adjunctive corticosteroids was 0.56 (95% CI: 0.32 to 0.98) at one month and 0.68 (95% CI: 0.50 to 0.94) at 3 to 4 months of follow-up.In 2015 Ewald et al. [107], which have the same authors list with Briel et al., indicated that RR for overall mortality for adjunctive corticosteroids were 0.56 (95% CI: 0.32 to 0.98) at one month and 0.59 (95% CI: 0.41 to 0.85) at three to four months of follow-up.However, the number and size of trials of two recent studies were small (six eligible studies).Also, we found that ART in HIV/PCP-positive patients was used three times more than in HIV-positive PCP-negative patients (OR: 3.356; 95% CI:0.785 to 14.349)(Table 2).Bucher et al. [104] reported that 80.5% of their studied patients had received ART.
Here we indicated that HIV-positive men had a 7% higher chance rate for PCP than women (OR:1.073;95% CI:0.674 to 1.706)(Table 2).Therefore, gender is not a potent risk factor for PCP among HIV-positive patients.However, Wasserman et al. [101] indicated that 39.6% of their study population were men.Also, SMD analysis of 1,583 PCP patients among 2,044 HIV-positive cases revealed no significant difference between HIV/AIDS patients with PCP and without PCP (SMD: -0.140; 95% CI:-0.315 to -0.034).Our SMD analysis showed that BDG serum mean levels in HIV/PCP patients were higher than in HIV-positive PCP-negative cases.Despite CD4 + T cells and LDH, no difference was observed in mean serum levels among the two groups.Bucher et al. [104] found that their studied patients' mean CD4 + T cell counts ranged from 51 to 200 cells/mm3 (group mean, 115 cells/mm3).We found that HIV-positive smokers and tuberculosis patients are twice more susceptible to PCP.De et al. [108] investigated the influence of smoking cessation on PCP incidence in HIV patients.They indicated no evidence to support that smoking increased the incidence of PCP.However, they reported that current smokers were at higher risk of bacterial pneumonia than current non-smokers (HR: 1.73; 95%CI: 1.44 to 2.06).

Conclusion
Now, PCP is still a serious health concern for people living with HIV/AIDS or other conditions with a weakened immune system.The exact number of HAP cases is challenging to estimate because there is no national surveillance program in different countries.We reported a high prevalence, risk, and mortality rates of PCP among the HIV-positive population.We concluded that, despite ART and prophylactic therapy, prevalence and mortality rates of HAP remained high.Therefore, the control and management strategies should be revised and updated by health policy-makers on a worldwide scale.For better management and understanding of the epidemiology and characteristics of this coinfection, designing a large-scale meta-analysis is recommended every three years.

Table 3 . The intercontinental distribution of HIV-associated PCP.
[102]I: 8 to 10) after 2005.Another study by Wills et al.[102]conducted a systematic review and meta-analysis to evaluate P. jirovecii prevalence in African HIV-positive adults with or without respiratory symptoms.They reported a prevalence rate of 19% (95% CI: 12 to 27) among 3,583 symptomatic and a 9% [95% CI: 0 to 45] prevalence rate among 140 asymptomatic adults.They concluded that despite increased access to local HIV services, P. jirovecii remains common in Africa.